So for the third stage play, they released a single, Saikai Aizu, which has recordings featuring only half the cast, so there is a Flower Version and a Star Version, Flora and Claire respectively. And according to these, Karen, Claudine, Junna, Futaba, Claudine, and Mahiru are Flora, and Hikari, Maya, Nana, and Kaoruko are Claire.
This matches up with what we saw in the show, with Hikari/Karen, and Maya/Claudine being confirmed Claire/Flora pairs, so it's a safe assumption to me at least.
Now we don't really know much about Claire or Flora. They are separated and only meet once a year, Claire lost her memories, Claire likes Blue and Flora has bad taste in fashion, but like we don't know their personalities at all. All we know is that Claire is the lead and Flora is the supporting lead. But the thing I am going to focus on is their fates.
Flora gets blinded and falls from the tower while Claire is trapped alone in the tower with her newfound knowledge but mostly regret.
The Claires in the Show are all trapped. Maya has resigned herself to a lonely life at the top. Nana stays in the time loops because she's scared of the future. Kaoruko feels burdened by her responsibilities as the future head of the Senka-Ryu school and rebelled by enrolling in Seisho. And Hikari literally ends up trapped in the underground stage for months after the Audition.
Meanwhile the Floras have all been blinded and fell. Claudine was so starstruck by Maya that she literally can't see her Maya ever losing to anyone, including herself. Futaba was ranked at the bottom of the class when they first enrolled and that shame eats at her, which is one of the reasons she pushes herself so hard in the Auditions. Junna laments how no matter how hard she worked, she could never catch up to Maya or Claudine, fighting in the shadows against Karen in their rematch instead of in the spotlight like a true Stage Girl. Mahiru claims that she has no glimmer, and that she has to rely on Karen's, which means she couldn't see how amazing she was until after the Revue of Jealousy. And Karen is blindsided by Hikari's betrayal at the end of the Auditions, quite literally falling from the tower.
So Mahiru is a Flora, at least in my opinion. But the odd thing is that her Claire is Karen, who is also a Flora. And the reason for that is because being Flora or Claire isn't static, it changes every Revue where they're fighting to become the lead.
In the Auditions, they use weapons made of their brilliance, and they aim to cut the star button of their opponent to make their cape fall. It's a metaphor, but also literal. In the Revue of Promise, Futaba can't bring herself to swing her Halberd since Kaoruko is just that dazzling, it blinds her. Every Revue is won by a Stage Girl overpowering another with their glimmer, with the winner rising while the loser remains at the bottom of the stage. But in the end, the ultimate winner of the Audition ended up trapped in the underground stage forever. And even before Hikari, Nana was the only ones who knew the truth of the Auditions. It's isolating at the top.
But that's just for the Starlight Auditions, there is another set of Revues in the Movie, and honestly I guess they sorta fit this pattern kinda okay as well.
In the Revue of Resentment, Kaoruko is blinded by Futaba's glimmer, which is why she doesn't swing her Naginata and falls off the tower. But Futaba goes down with her, because she knows her fate is tied to Kaoruko's, no matter how far apart they are, she's stuck with Kaoruko in the end. In the Revue of Competition, after being dropped from a 101 floor tower by Mahiru, the end of the Revue has Hikari tells her that she was a real stage actress, and Mahiru renews her oath, that she's going to keep acting, even if it's painful, because she wants to aim straight for her brilliant self. In the Revue of Hunting, Junna's uses her continued resolve to keep looking for the stage where is the lead to cut down Nana's production, and it ends with a weeping Nana admitting that Junna is dazzling. And in the Revue of the Soul, Maya loses while admiring Claudine's beauty, and agrees with Claudine that they will remain rivals for eternity.
So once again, the losers of the Revues are blinded by the winner's brilliance, which is why they fall and end up losing something. Kaoruko gives up on cutting ties with Futaba, Hikari confides in Mahiru that she had been scared of Karen's brilliance and decides to stop running away, Nana realizes that her Junna-chan no longer exists and her final reproduction has come to an end, and Maya has to give up on her Empty Vessel of God plan for her future because Claudine showed her a brilliance far greater than what Maya imagined. The Floras lose both because they were blinded by the Claire's brilliance, but also because the Claire had a stronger vision of their future by the end of the Revue, and they are sticking to that path.
However, there is one exception to this general rule that Claires are the winners of the Revue. Karen wins the Revue of Astral Sins, and she's Flora. Hikari was trapped in the underground stage since she knew everyone would lose their glimmer otherwise, and Karen was blindsided and didn't understand what happened. But like, lets be real, this Revue is the rewritten version of Starlight where Flora climbs up the tower again. Flora's the lead in that version, and the Revues are meant to decide the star, so that's why Claire loses.
Anyways back to the Movie Revues, Hikari is waiting for Karen at the top of the tower after she fell from the tower, and Karen loses after saying she can't take her eyes off of Hikari and Hikari stabs her with a knife pierces Karen with her brilliance. So it makes sense that Hikari is Claire and that's why she won.
But the issue with that is in the rest of the Movie, Hikari is Flora and Karen is Claire. It's revealed that this entire time, Hikari has actually been blinded by Karen's Brilliance, which is why she had run away from both as a child and in their third year. Hikari has to descend into the underground stage this time, guided by the goddesses (or in this case just Mahiru), to find her partner after being blinded, just like Karen/Flora did in the rewrite when the rest of the class guided Karen down the underground stage.
And Karen waits for her at the top of the tower, with her newfound knowledge and regrets, that she only became a Stage Girl because of Hikari and that she has no stage after Starlight. But Karen's freed from the Tower, because Hikari returned for her, just like how Flora did for Claire in the rewrite.
There is no Claire between Hikari and Karen at the end of the movie, they are both Flora, blinded by the other's brilliance and doomed to fall, but rising up again to face each other anyways. Neither of them are trapped, they have a path forward, because the other freed them by coming back.
In fact, all of the winners of the Movie Revues are originally Floras. They all lost before, they were blinded by someone's brilliance and fell, unable to become the lead. Even when they win in the Movie, they aren't trapped, they're just sticking to what they decided at the start of the movie, they're still moving. Futaba wants to become a more brilliant Stage Girl so she can stand shoulder to shoulder with Kaoruko. Mahiru thinks she's a bad actor but keeps at it anyways. Junna thinks the stage where she is a lead is distant, but she's still aiming for it. Claudine's competition with Maya will never end.
They were all the Flora once who lost to Claire, but they came back and it freed both of them. Futaba gives Kaoruko her keys as a promise to return for them, Mahiru says she had always wanted to act with Hikari, Junna dreams of standing on stage with Nana again in the future. Claudine literally says she'll die as many times as it takes if it means she can challenge Maya again.
In order to move onto the next stage, you have to be Flora. Otherwise you're trapped like Claire, unable to move on. You might get blinded, face setbacks and struggles, but you need to pick yourself up and try again, otherwise it's not the rewrite with a hopeful ending, it's the original tragedy.
Anyways this is a real long way of saying Mahiru, along with everyone else in the main cast of Revue Starlight, is Flora by the end of the Movie. Hope that answers your question.